Pneumatic counterbalance for crank motion machines



Sept. 12, 1939. w BURNS 2,172,346

PNEUMATIC COUNTERBALANCE FOR CRANK MOTION MACHINES Filed May 1, 1937 2 Sheets-Sheet l BY w r W ATTORNEYS.

w. E. BURNS 2,172,346

PNEUMATIC COUNTERBALANGE FOR CRANK MOTION MACHINES Sept. 12, 1939.

Filed May 1 1937 2 Sheets-Sheet 2 mm, A m m. V 4 f N M m A\\\m m5 v T l E mm ml 3 A Wk mfi F W w .J .a, M 4 I r A Y QR B .m U NR. W WV mm Q. MIN) h QM, bvkm. \O. lown: a w \8 1| '1 l mm o o 0 m1 O\ O/ \O: mm, a w qmwfi ww r m, N.

hm W n wm 4 Patented Sept. 12, 1939 UNITED STATES PATENT OFFICE PNEUMATIC COUNTERBALANGE FOR CRANK MOTION MACHINES Application May 1, 1937, Serial No. 140,211

3 Claims.

provide pneumatic counterbalancing means of the above character whereby the inertial forces of a reciprocating mechanism are gradually opposed and cushioned as the mechanism approaches the ends of its stroke in opposite directions, and whereby the mechanism, on coming to rest at the end of each stroke, is given a certain impulse to aid in starting on its return stroke; thus the counterbalance operates not only to cushion the reciprocating action, but also to lessen the amount of power required for the operation of the machine.

It is also an object of this invention to provide a pneumatic counterbalance of the above stated character in which the cushioning effect and the return impulse force may be varied or regulated to suit different conditions and speeds of reciprocation of the mechanism with which the device is used.

It is a further object of this invention to provide a counterbalance means of the above stated character which will operate also to take up slack that may be incident to wear on bearings or connections, and thus make possible a more accurate travel of the reciprocating devices.

Other objects of the invention reside in the details of construction, in the combination of parts and mode of operation as will hereinafter be fully described.

In accomplishing the above and other objects of the invention, 1 have provided the improved details of construction, the preferred forms of which are illustrated in the accompanying drawings, wherein Fig. 1 is a sectional detail of a part of a can body maker, illustrating the use of a pneumatic counterbalance embodied by the present invention in connection with the reciprocating feed bars of the machine.

Fig. 2 is a plan view of a part of the reciproeating feed mechanism of the body maker with which the counterbalance is associated.

Fig. 3 is an enlarged, horizontal section of the pneumatic counterbalance as seen on the line 2-2 in Fig. 1.

Fig. 4 is a cross section on the line 44 in Fig. 3.

Fig. 5 is a cross section on the line 5-5 in Fig. 3.

For purpose of explaining the use of the present pneumatic counterbalance, I have illustrated it in connection with a can body maker, and while it is believed novel in this specific use, it is not intended that the invention be confined thereto.

Referring more in detail to the drawings- In Fig. 1 has been illustrated a part of a can body maker of a type quite extensively used in the can making industry, and in which I designates a cylindrical forming horn about which the body blanks from which the cans are made, and not herein shown, are shaped to their final body form. 2 designates a slide that is reciprocally mounted on a fixed guide rail 3 and to which slide parallel feed bars 44 are secured through the mediacy of a cross bar 5 which is best shown in Fig. 2. The feed bars are equipped with means not here-in shown in detail, whereby the can body blanks are advanced in succession, and by intermittent movements, to the forming horn, at which station'wing clamps operate to form the blanks about the horn and to join the ends in a permanent seam; these operations being quite well understood in the can making art.

Since the details of the construction of the body maker are of no particular import to the claims hereinafter to be made, they will not be further described. It will be understood, however, by reference to Fig. l of the drawings, that the frame structure of the body maker is mounted upon a base plate 6, and the feed bars 44 are mounted by folder housings, as designated at i, which, in turn, are supported on a bed 8.

The reciprocal action of the feed slides 44 and those parts directly associated therewith, is effected through connection with a rotatably driven crank shaft that is revolubly mounted in the main frame structure. The means for driving this crank shaft is not illustrated; however, it will be understood that in the ordinary operation of the machine, this shaft rotates at a uniform speed. Incidentally, it will be mentioned that this crank shaft, through the mediacy of a pitman ll, operates the seam closing hammer l2, which, as seen in Fig. 1, is reciprocally mounted in suitable guides, as at 13.

A link is attached at one end to the crank shaft H! and, at its opposite end, is pivotally attached, as at IE, to the lower end of a lever arm ll, rigidly fixed on a cross shaft 18. Shaft 18 is the arm 20. This connection provides that the oscillating action of the cross shaft l8, imparted thereto by the rotating action of the crank ID, will effect a reciprocal action of'the slide 2 on the guide rail 3, and the slide, in turn, will effect the reciprocal action of the feed bars 44.

Persons familiar with the can making art and the construction of machines of thistype, will realize that when the bars 4-4 are reciprocating at high speed, say for example, from 250 to 300 times per minute, and since they are of considerable weight, there will be a considerable amount of inertial force expended at the end of each stroke, and that these forces will produce a considerable amount of vibration in the machine and will also bring about wear on the parts. Furthermore, since, in machines of this kind, the feed bars must move with a certain degree of accuracy, it will be understood that this cannot be absolutely maintained by reason of the fact that there will be'certain yielding or spring in the parts operating under high speed, and wear will permit parts to get out of adjustment, and this is detrimental to accuracy in the finished can body.

In view of the above, it has been the principal object of this invention to provide a counterbalancing means for the reciprocating mechanisms that will oppose the inertial forces as the controlled mechanisms near the end of a stroke in opposite directions, and as the parts come to rest at the end of each stroke, will act to impart a force in the opposite direction to aid in operation.

The present counterbalance, as best shown in Figs. 1 and 3, comprises a pair of axially alined, spaced air cylinders 30 and 30, closed at their outer ends by head plates 3| and 3| respectively, but open at their inner ends. These two cylinders are flanged and bolted, as seen in Fig. 4, to a base 32 which, in turn, is bolted to the base plate 6. Slidably mounted in the cylinders, respectively, are pistons 33 and 33, connected rigidly together by a rod 35. Fixed on the rod, intermediate its ends and between the cylinders, is a block 36, having a flanged base 31 reciprocally slidable in a guide groove. 38, in a plate 39 mounted on the base 32 between the cylinders; the block flange being held in the guideway by plates 4040, which overlap its opposite edges,.as seen in Fig. 5.

Fixedto the cross shaft [8, which is disposed directly above a point midway between the cylinders and transversely of the shaft 35, is a lever arm 45, which, at its lower end, has pivotal connection through the mediacy of a cross bolt 46, with slides 41 slidably fitted in vertical guides in the block 36 that is fixed to the connecting rod 35. g It will be understood that, with the above described connections, the oscillating action of the shaft l8 will effect the reciprocation of the pistons in their respective cylinders, and it will be understood also that as each piston moves toward the closed end of its cylinder, it will effect the compressing of trapped air, which will cushion the travel of the reciprocating parts connected with the shaft [8, and will oppose the inertial forces of the parts.

By reference to Figs. 3 and 4, it will be observed that each of the air cylinders is provided, in its side walls, toward its open end, with a plurality of air slots 50, which will be uncovered when the piston moves outwardly beyond a. certain limit, permitting the cylinder to be charged with air. Also, when the piston moves inwardly, it will, after a certain travel, close off these air slots to trap the air for forming the cushion. It will also be noted,"by reference to Fig. 3, that, associated with each of the air cylinders, is' an auxiliary chamber 60 located at one side of the cylinder,

and preferably integral therewith. These auxiliary chambers are of cylindrical form, and each has a closure plug 65 slidably fitted therein. At its inner end, each of the auxiliary chambers communicates with the air cushion or closed end of its corresponding cylinder 30 or 30'; the communicating passages being indicated at 68. The closure plugs 55 are adjustable inwardly or outwardly in their respective chambers to vary the volume of the chamber, and the means for holding the plugs at set positions, as illustrated in Fig. 4, comprises set screws 10, which are threaded through the chamber walls to seat at their inner ends in any one of a plurality of spaced encircling grooves 12 in the plug members. If it is desired toincrease the capacity of an auxiliary chamber, the set screw is loosened, and the plug pulled outwardly. Then, the set screw is tightened to hold the plug at the set position.

Assuming that the pneumatic counterbalancing means is so constructed, and that it is connected with the mechanism as herein illustrated and described, it is apparent that in the normal operation of the body maker, the cushioning action afforded through the mediacy of the pistons and cylinders will take place at the end of each stroke of the feed bars. As a piston moves toward the end of its cylinder, the air cushion is gradually built up, and therefore the forces opposing the inertial forces of the reciprocating parts and the retarding action of the feed bar is gradual and Without shock. Furthermore, when the reciprocating parts reached the end of a stroke in one direction the compressed air in the cylinder acts against the piston and serves as an impelling :force toaid in the return of the reciprocating parts in the opposite directions. 7

If it should be desired. to increase or decrease the retarding action, this is accomplished by an adjustment of the plugs in the auxiliary chambers, which will decrease or increase the volume of the air cushioning space.

The particular advantage of this device in a can body machine is that it eliminates, to a material extent, the vibration in the machine. It takes up the slack that may result from wear in bearings, and it insures a more accurate determination of the travel of the reciprocating parts.

Devices of this character in various sizes may be employed in connection with various kinds of machines, and are especially useful where the reciprocating parts are heavy and moving at big speed.

Having thus described my invention, what I claim as new therein and desire to secure by Letters Patent is 1. In a can body maker having a reciprocating feed bar mechanism and an oscillating shaft transversely of and operatively connected to reciprocate the said feed bar mechanism, a 75 pneumatic counterbalance comprising a pair of cushioning cylinders in fixed positions, pistons reciprocally fitted therein, a rod connecting the pistons, an arm fixed on the oscillating shaft and having operative connection with the piston rod whereby the pistons are caused to reciprocate in their cylinders in accordance with the reciprocation of the feed bar mechanism, and confined in their stroke to the limits of their respective cylinders whereby air cushions are built up alternately in the cylinders to oppose the inertial forces of the said mechanism at the ends of its stroke in opposite directions said cylinders having air ports to be uncovered by the pistons at the end of the stroke in one direction for establishing atmospheric pressure in the cylinder.

2. In a can body making machine having a reciprocally movable feed bar mechanism and a driven shaft operatively connected to reciprocate the said mechanism, two cooperating air cushioning cylinders closed at their outer ends and open at their inner ends, pistons reciprocally mounted in the cylinders, a rod operatively connecting the pistons in opposed relationship, and having an operating connection with the driven shaft whereby the pistons are reciprocated in timing with the feed bar mechanism and are confined in their travel to the limits of their respective cylinders; said cylinders having relief ports in their side walls near their open ends adapted to be uncovered by the corresponding pistons traveling toward the open ends of the cylinders to admit air into the cylinders to establish atmospheric pressure therein, and to be closed by their respective pistons traveling in the reverse direction for compressing the air admitted through the ports to resist and counterbalance the inertial forces of the reciprocating parts; said ports of the cylinders being so arranged that those of one cylinder are opened after the ports in the other have been closed.

3. A device as in claim 2 wherein each cylinder is provided with an auxiliary air chamber in open communication therewith and means is provided in each chamber for varying its capacity independently of the capacity of the other chamber.

WILFORD E. BURNS. 

